Preliminary Study On Flavor Formation Mechanism Of Pan-frying Grass Carp And Design Of 1000 Tons Fish Products Production Plant

Pan-frying is a convenient and efficient cooking method,which can provide processed food with good sensory enjoyment and mellow flavor in a short time because of its efficient ripening.However,the traditional and mostly empirical pan-frying process lacks scientific and standardized guidance,resulting in great differences in taste,flavor and nutrition of fish fillets made by different processes.Previous studies have showed that the flavor substances promoted by pan-frying mainly depended on the reaction time and temperature,the content of amino acids and fatty acids.Pan-frying exposed to high temperature and long time can promote the formation of a series of small molecular volatile substances,especially lipid oxidation flavor,and finally endow the fish fillets with burnt,aldehyde and fat flavor.However,its promotion mechanism is ambiguous and needs to be further studied.Therefore,the effects of pan-frying conditions on fish quality parameters,flavor substances and flavor precursors,the key intermediates of promoting the formation of fish flavor and molecular mechanism of lipid oxidized flavor substances were clarified through taking grass carp and soybean oil as the research object and heating medium,respectively.1、The quality parameters and flavor substances of fried fish were determined by gas chromatography-mass spectrometry（SPME-GC-MS）.The results show a better sensory evaluation is that when the pan-frying temperature is 160℃or 180℃,the time is no more than 8 min;while is 200℃or 220℃,the time is no more than 6 min.Flavor substances formed at low temperature and short time were lipid oxidation substances,while high temperature or long time pan-frying would lead to the formation of a small amount of Maillard reaction flavor substances（pyrazine,furan,etc.）.According to the analysis of PCA and PLS-DA,the top 11 lipid oxidizing flavor substances are hexanal or hexanol,1-octen-3-ol,nonanal or nonanol,1-penten-3-ol,2-nonone,2-octen-1-ol,heptanol,2,3-octanedione,octanal or octanol,3-nonen-1-ol and 2,4-decadienal.2、The flavor precursors formed during the frying of grass carp were studied by spectroscopy and chromatography.The results showed that the free amino acids,peroxide value（POV）and carbonyl value（CV）in fish fillets was increased significantly with the increase of frying time.At the same time,the content of C18:2n-6 was increased significantly,while C18:1,C20:4n-6 and C22:6n-3 decreased,of which the decrease proportion of C20:4n-6 was the largest.It was found that arachidonic acid（ARA）was the precursor of 2-nonone,3-nonen-1-ol,2-octen-1-ol,1-octen-3-ol,2,3-octadione and 2,4-decadienal.The second is oleic acid（OA）,which can form a certain amount of hexanal,heptanal,octanal and nonanal after heat treatment.The third is linoleic acid（LA）,which is the second main precursor of 2,4-decadienal.3、Both Nano ESI-MS/MS and LC-TOF-MS/MS were applied to study the critical intermediates and their decomposition positions in fried fish fillets.Nine aldehydes and ketones were detected in fried fish,and their contents were all increased,except for acetone.Furthermore,23 kinds of hydroxyl fatty acids and hydroperoxides were detected in fish fillets fried at 160℃for 6 min,while 16 kinds of hydroxyl fatty acids and hydroperoxides in fish fillets fried at 200℃for 2 min.Among them,11-and 14-hydroxy arachidonic acid（11-HETE,14-HETE）were only monitored by LC-TOF-MS/MS.The corresponding relationship between critical intermediates and main flavor substances in fried fish is as follows:（1）The main precursor of hexanal is ARA,which is oxidized to 14-,15-HETE and formed through C₁₄-C₁₅α/β-homolysis;（2）The main precursor of 1-octen-3-ol is ARA,which is oxidized to 12-HETE and formed through C₁₂-C₁₃β-Homolysis,and subsequent double bond rearrangement,secondary oxidation;（3）The main precursor of nonanal is OA,which is oxidized to 10-HPOME and formed through C₉-C₁₀α-homolysis;（4）The main precursor of 1-penten-3-ol is ALA,which is oxidized to 13-HPOTr E and formed through C₁₃-C₁₄β-homolysis,and subsequent double bond rearrangement,secondary oxidation.（5）The main precursors of 2-nonone are LA and ARA,which are oxidized to 9-HPODE and 11-HETE and formed through C₉-C₁₀in 9-HPODE and C₁₁-C₁₂in 11-HETEβ-homolysis,and subsequent double bond rearrangement and secondary oxidation;（6）The main precursor of 2-octen-1-ol is ARA,which is oxidized to 12-HETE and formed through C₁₂-C₁₃β-homolysis in epoxide formed by dehydration;（7）The main precursor of heptanol is OA,which is oxidized to11-HPOME and formed through C₁₁-C₁₂β-homolysis in epoxide formed by dehydration;（8）The main precursor of octanal is OA,which is oxidized to11-HPOME and formed through C₁₀-C₁₁α-homolysis;（9）The main precursor of3-nonen-1-ol is ARA,which is oxidized to 12-HETE and formed through C₁₁-C₁₂α-homolysis;（10）The main precursor of 2,4-decadienal is ARA,which is oxidized to11-HETE and formed through C₁₀-C₁₁α-homolysis;（11）2,3-octanedione:its precursor was not found.4、According to the processing of fried fish steaks,the factory design of 1000 t fried fish steaks is carried out.The results show that the annual output of 1000 t fried fish steak needs 1538.46 t fresh grass carp,385 t soybean oil,16.92 t cooked sesame,6.34 t peanut powder,6.34 t soybean powder,50.76 t chili oil,16.92 t chili powder,2.54 t perilla juice,0.85 t flavored sodium nucleotide,0.85 t ethyl maltol,20 million inner bags,200000 cartons,11007.5 t annual water consumption and 163700 kwh annual power consumption.The total annual cost is 4874.41 million yuan,the annual sales revenue is 7000 million yuan,the annual net profit is 1404.74 million yuan,and the annual net profit margin is 20.06%.